Investigation and management of residual sleepiness in CPAP-treated patients with obstructive sleep apnoea: the European view

Excessive daytime sleepiness (EDS) is a major symptom of obstructive sleep apnoea (OSA), defined as the inability to stay awake during the day. Its clinical descriptors remain elusive, and the pathogenesis is complex, with disorders such as insufficient sleep and depression commonly associated. Subjective EDS can be evaluated using the Epworth Sleepiness Scale, in which the patient reports the probability of dozing in certain situations; however, its reliability has been challenged. Objective tests such as the multiple sleep latency test or the maintenance of wakefulness test are not commonly used in patients with OSA, since they require nocturnal polysomnography, daytime testing and are expensive. Drugs for EDS are available in the United States but were discontinued in Europe some time ago. For European respiratory physicians, treatment of EDS with medication is new and they may lack experience in pharmacological treatment of EDS, while novel wake-promoting drugs have been recently developed and approved for clinical use in OSA patients in the USA and Europe. This review will discuss 1) the potential prognostic significance of EDS in OSA patients at diagnosis, 2) the prevalence and predictors of residual EDS in treated OSA patients, and 3) the evolution of therapy for EDS specifically for Europe

Iterated maps for clarinet-like systems

The dynamical equations of clarinet-like systems are known to be reducible to a non-linear iterated map within reasonable approximations. This leads to time oscillations that are represented by square signals, analogous to the Raman regime for string instruments. In this article, we study in more detail the properties of the corresponding non-linear iterations, with emphasis on the geometrical constructions that can be used to classify the various solutions (for instance with or without reed beating) as well as on the periodicity windows that occur within the chaotic region. In particular, we find a regime where period tripling occurs and examine the conditions for intermittency. We also show that, while the direct observation of the iteration function does not reveal much on the oscillation regime of the instrument, the graph of the high order iterates directly gives visible information on the oscillation regime (characterization of the number of period doubligs, chaotic behaviour, etc.)

An active mute for the trombone

A mute is a device that is placed in the bell of a brass instrument to alter its sound. However, when a straight mute is used with a brass instrument, the frequencies of its first impedance peaks are slightly modified, and a mistuned, extra impedance peak appears. This peak affects the instrument’s playability, making some lower notes difficult or impossible to produce when playing at low dynamic levels. To understand and suppress this effect, an active mute with embedded microphone and speaker has been developed. A control loop with gain and phase shifting is used to control the damping and frequency of the extra impedance peak. The stability of the controlled system is studied and then the effect of the control on the input impedance and radiated sound of the trombone is investigated. It is shown that the playability problem results from a decrease in the input impedance magnitude at the playing frequency, caused by a trough located on the low frequency side of the extra impedance peak. When the extra impedance peak is suppressed, the playability of the note is restored. Meanwhile, when the extra impedance peak is moved in frequency, the playability problem position is shifted as well

Caractérisation du rayonnement de la table d'harmonie d'un piano droit

In this paper we present a simple model of a upright piano soundboard as a baffled isotrope plate. This model enables us to calculate analytically the sound radiation of the soundboard in the back semi-infinite space of the piano and to find the frequency threshold of the appearance of the lobe of maximum pressure for each mode. These results are compared with measurements on a real upright piano. We find that the resonance frequency of the modes are less than this frequency threshold, therefore the maximum sound radiation can not occur. The pattern of the sound radiation appears to follow the theoretical model but more experiments will be required to show this clearly

CORDE FROTTÉE : TYPE PARTICULIER DE MOUVEMENT A DEUX VITESSES OBSERVÉ SOUS L'ARCHET

Des mouvements de la corde sous l'archet pour lesquels le point représentatif alterne plus d'une fois au cours d'un cycle entre deux vitesses ont été observés. Les conditions à satisfaire pour les obtenir sont étudiées à partir d'une simulation informatique de la corde frottée.Motions of the bowed string at the point where the bow is located were observed. The satisfying conditions to obtain these motions are studied with a computer simulation of the bowed string

Experimental validation of adjusting the resonances of a simplified bass clarinet through modal active control.

This paper reports the experimental results of modifying the resonances of wind instruments using modal active control. Resonances of a simplified bass clarinet (a cylindrical tube coupled to a bass clarinet mouthpiece including a reed) are adjusted either in frequency or in damping in order to modify its playing properties (pitch, strength of the harmonics of the sound, transient behavior). This is achieved using a control system made up of a collocated loudspeaker and microphone linked by an observer, which contains a model of the system, and a controller. Modifications of the transfer function, input impedance and radiated sound of the instrument are obtained

In-Vitro and Numerical Investigations of the Influence of a Vocal-Tract Resonance on Lip Auto-Oscillations in Trombone Performance

International audienceControlling the acoustic impedance of the upstream airways in brass instrument performance may bean important factor influencing the efficiency of the sound production process. Because of the complexcharacteristics of the lip-valve oscillator, the conditions under which a vocal-tract resonance may be favorableto the sustain of lip auto-oscillations are not easy to determine. In order to investigate this aspect ofbrass performance, an experimental method based on an active control approach is applied to an artificialtrombone player system in order to simulate the influence of a vocal-tract resonance at the playing frequency.By varying the amplitude and phase characteristics of this upstream impedance load, we investigatethe acoustical influence of this resonance on lip vibrations and on the acoustic pressure generated in theinstrument. The observations reveal that variations of the phase difference between the downstream andupstream impedance induce significant variations of the playing frequency. An optimal phase tuning pointcharacterized by a maximum of downstream acoustic pressure at the input of the instrument, and uncorrelatedto a maximum of downstream input impedance, is identified. These experimental results are comparedwith numerical simulations, both of which produce similar findings. The optimal tuning point appears tobe partly related to the displacement of the playing frequency close to a mechanical resonance of the lips.This induces a greater “efficiency" of the lip-valve system, hence maximizing the acoustic flow generatedinto the instrument while other control parameters (quasi-static mouth pressure, lip tension) are maintainedconstant. In addition to an exploration of acoustical influence of the vocal tract, this experimental methodhence offers promising perspectives for the study of artificial lips under playing conditions